U.S. patent application number 11/874651 was filed with the patent office on 2008-04-24 for liquid crystal display.
Invention is credited to Sang-Woo KIM, Yi Li.
Application Number | 20080094546 11/874651 |
Document ID | / |
Family ID | 39317549 |
Filed Date | 2008-04-24 |
United States Patent
Application |
20080094546 |
Kind Code |
A1 |
KIM; Sang-Woo ; et
al. |
April 24, 2008 |
LIQUID CRYSTAL DISPLAY
Abstract
A liquid crystal display includes a first display panel
including a first substrate and a lower alignment layer formed on
the first substrate, a second display panel that includes a second
substrate facing the first substrate to maintain a predetermined
cell gap between the substrates and an upper alignment layer formed
on the second substrate, a liquid crystal layer provided between
the first and second display panels, a wide view polarizer and a
lower polarizer sequentially attached to the outside of the first
display panel, and an upper polarizer attached to the outside of
the second display panel. An absorption axis of the wide view
polarizer is inclined with respect to an absorption axis of the
lower polarizer by 45.degree.. An absorption axis C' inclined with
respect to the absorption axis A' of the lower polarizer by
45.degree. is interposed between the lower polarizer and the liquid
crystal panel in the backlit electrically controlled birefringence
(ECB) mode.
Inventors: |
KIM; Sang-Woo; (Suwon-si,
KR) ; Li; Yi; (Yongin-si, KR) |
Correspondence
Address: |
MACPHERSON KWOK CHEN & HEID LLP
2033 GATEWAY PLACE
SUITE 400
SAN JOSE
CA
95110
US
|
Family ID: |
39317549 |
Appl. No.: |
11/874651 |
Filed: |
October 18, 2007 |
Current U.S.
Class: |
349/96 |
Current CPC
Class: |
G02F 1/1393 20130101;
G02F 1/133567 20210101; G02F 1/133528 20130101; G02F 1/133531
20210101 |
Class at
Publication: |
349/096 |
International
Class: |
G02F 1/1335 20060101
G02F001/1335 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 18, 2006 |
KR |
10-2006-0101243 |
Claims
1. A liquid crystal display comprising: a first display panel
including a first substrate and a lower alignment layer formed on
the first substrate; a second display panel including a second
substrate and an upper alignment layer formed on the second
substrate, the second substrate facing the first substrate to
maintain a predetermined cell gap between the substrates; a liquid
crystal layer provided between the first and second display panels;
a wide view polarizer and a lower polarizer sequentially attached
to the outside of the first display panel; and an upper polarizer
attached to the outside of the second display panel, wherein an
absorption axis of the wide view polarizer is inclined with respect
to an absorption axis of the lower polarizer by 45.degree..
2. The liquid crystal display of claim 1, wherein a lower rubbing
axis of the lower alignment layer is reversed and parallel to a
rubbing axis of the upper alignment layer.
3. The liquid crystal display of claim 2, wherein the lower rubbing
axis is reversed and parallel to the absorption axis of the wide
view polarizer.
4. The liquid crystal display of claim 3, wherein the liquid
crystal layer is formed of liquid crystal that has positive
refractive anisotropy.
5. The liquid crystal display of claim 4, wherein the wide view
polarizer includes a compensation film and wide view
supporters.
6. The liquid crystal display of claim 5, wherein the compensation
film is an O-plate.
7. A liquid crystal display comprising: a first display panel
including a first substrate and a lower alignment layer formed on
the first substrate; a second display panel including a second
substrate and an upper alignment layer formed on the second
substrate, the second substrate facing the first substrate to
maintain a predetermined cell gap between the substrates; a liquid
crystal layer provided between the first and second display panels;
a lower polarizer attached to the outside of the first display
panel; and a wide view polarizer and an upper polarizer
sequentially attached to the outside of the second display panel,
wherein an absorption axis of the wide view polarizer is inclined
with respect to an absorption axis of the upper polarizer by
45.degree..
8. The liquid crystal display of claim 7, wherein a lower rubbing
axis of the lower alignment layer is reversed and parallel to an
upper rubbing axis of the upper alignment layer.
9. The liquid crystal display of claim 8, wherein the upper rubbing
axis is reversed and parallel to the absorption axis of the wide
view polarizer.
10. The liquid crystal display of claim 9, wherein the liquid
crystal layer is formed of liquid crystal, which has positive
refractive anisotropy, in an electrically controlled birefringence
(ECB) mode.
11. The liquid crystal display of claim 10, wherein the wide view
polarizer includes a compensation film and wide view
supporters.
12. The liquid crystal display of claim 11, wherein the
compensation film is an O-plate.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to and the benefit of
Korean Patent Application No. 10-2006-0101243 filed in the Korean
Intellectual Property Office on Oct. 18, 2006, the entire contents
of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention relates to a liquid crystal
display.
[0004] 2. Description of the Related Art
[0005] Currently, liquid crystal displays are one of the flat panel
displays that are most widely used. A liquid crystal display
includes two display panels on which field generating electrodes,
such as pixel electrodes and a common electrode, are formed with a
liquid crystal layer interposed between them. When a voltage is
applied to the field generating electrodes to generate an electric
field, the alignment of liquid crystal molecules is determined and
controls the polarization of incident light to display images.
[0006] Liquid crystal displays are classified as backlit liquid
crystal displays that use a separate backlight as a light source,
and reflective liquid crystal displays that reflect external light.
A transreflective liquid crystal display, which can be converted
into a reflective or backlit liquid crystal display according to
demand, has been developed in recent years.
[0007] Liquid crystal displays may be classified according to mode
as vertical align (VA) mode, twisted nematic (TN) mode,
electrically controlled birefringence (ECB) mode on the basis of
the characteristics of the liquid crystal. The transmittance of the
liquid crystal in the ECB mode is higher than that of the liquid
crystal in the TN mode.
[0008] However, the luminance of the liquid crystal display in the
ECB mode is lower than that of the liquid crystal display in the TN
mode. In addition, the viewing angle of the liquid crystal display
in the ECB mode is also narrower than that of the liquid crystal
display in the TN mode.
[0009] Further, the liquid crystal display in the ECB mode is
generally provided in the form of a transflective liquid crystal
display in order to maximize the transmittance of the liquid
crystal display. However, the transreflective liquid crystal
display should be manufactured in a production line in which both
reflective and backlit liquid crystal displays are produced. For
this reason, the process of manufacturing the transflective liquid
crystal display is complicated, and more time is required to
manufacture the transflective liquid crystal display.
SUMMARY OF THE INVENTION
[0010] According to an exemplary embodiment of the present
invention, a liquid crystal display having a wide view
electrically-controlled birefringence (ECB) mode includes a first
display panel including a first substrate and a lower alignment
layer formed on the first substrate, a second display panel that
includes a second substrate facing the first substrate to maintain
a predetermined cell gap between the substrates and an upper
alignment layer formed on the second substrate, a liquid crystal
layer provided between the first and second display panels, a wide
view polarizer and a lower polarizer sequentially attached to the
outside of the first display panel, and an upper polarizer attached
to the outside of the second display panel. The absorption axis of
the wide view polarizer is inclined with respect to an absorption
axis of the lower polarizer by 45.degree..
[0011] Further, the lower rubbing axis of the lower alignment layer
may be reversed and parallel to the rubbing axis of the upper
alignment layer. Furthermore, the lower rubbing axis may be
reversed and parallel to the absorption axis of the wide view
polarizer. In addition, the liquid crystal layer may be formed of
liquid crystal, which has positive refractive anisotropy, in an
electrically controlled birefringence (ECB) mode. The wide view
polarizer may include a compensation film and wide view supporters,
and the compensation film may be an O-plate.
[0012] According to another exemplary embodiment of the present
invention, a liquid crystal display includes a first display panel
including a first substrate and a lower alignment layer formed on
the first substrate, a second display panel that includes a second
substrate facing the first substrate to maintain a predetermined
cell gap between the substrates and an upper alignment layer formed
on the second substrate, a liquid crystal layer provided between
the first and second display panels, a lower polarizer attached to
the outside of the first display panel, and a wide view polarizer
and an upper polarizer sequentially attached to the outside of the
second display panel. The absorption axis of the wide view
polarizer is inclined with respect to the absorption axis of the
upper polarizer by 45.degree..
[0013] Further, a lower rubbing axis of the lower alignment layer
may be reversed and parallel to a rubbing axis of the upper
alignment layer. The upper rubbing axis may be reversed and
parallel to the absorption axis of the wide view polarizer. The
liquid crystal layer may be formed of liquid crystal that has
positive refractive anisotropy, in an electrically controlled
birefringence (ECB) mode. Further, the wide view polarizer may
include a compensation film and wide view supporters, and the
compensation film may be an O-plate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a layout view of a liquid crystal display
according to an exemplary embodiment of the present invention.
[0015] FIG. 2 is a cross-sectional view of the liquid crystal
display shown in FIG. 1 taken along the line II-II.
[0016] FIG. 3 is a cross-sectional view of the liquid crystal
display shown in FIG. 1 taken along the line III-III.
[0017] FIG. 4 is a detailed view illustrating the structure of a
liquid crystal panel including display panels and a liquid crystal
layer interposed therebetween, a lower polarizer, a wide view
polarizer, and an upper polarizer.
[0018] FIG. 5 is a perspective view illustrating the angular
relationship between the polarizer and the alignment layer shown in
FIGS. 2 and 4.
[0019] FIG. 6 is a view illustrating the angular relationship of a
liquid crystal display shown in FIG. 5, as seen from above.
[0020] FIG. 7 is a view illustrating the three-dimensional optical
characteristic obtained from a simulation of an exemplary
embodiment shown in Table 1.
[0021] FIG. 8 is a view illustrating the three-dimensional optical
characteristic obtained from measurement using a iconoscope while
the difference (.DELTA.nd) in phase is set to 300.96 in the
exemplary embodiment of the present invention, with a picture
showing viewing angles in a black state, a picture showing viewing
angles in a white state, and a view showing contrast ratios
(C/R).
[0022] FIG. 9 is a perspective view illustrating the angular
relationship between a polarizer and an alignment layer of a liquid
crystal panel according to another exemplary embodiment of the
present invention.
[0023] FIG. 10 is a view illustrating the angular relationship of
the liquid crystal display shown in FIG. 9, as seen from above.
DETAILED DESCRIPTION OF THE EMBODIMENTS
[0024] In the drawings, the thickness of layers, films, panels,
regions, etc., are exaggerated for clarity. Like reference numerals
designate like elements throughout the specification. It will be
understood that when an element such as a layer, film, region, or
substrate is referred to as being "on" another element, it can be
directly on the other element or intervening elements may also be
present. In contrast, when an element is referred to as being
"directly on" another element, there are no intervening elements
present.
[0025] First, a liquid crystal display according to an exemplary
embodiment of the present invention will be described in detail
with reference to FIGS. 1 to 3.
[0026] FIG. 1 is a layout view of a liquid crystal display
according to an exemplary embodiment of the present invention, FIG.
2 is a cross-sectional view of the liquid crystal display shown in
FIG. 1 taken along a line II-II shown in FIG. 1, and FIG. 3 is a
cross-sectional view of the liquid crystal display shown in FIG. 1,
taken along the line III-III shown in FIG. 1.
[0027] A plurality of gate lines 121 and a plurality of storage
electrode lines 131 are formed on an insulation substrate 110 that
is made of transparent glass or plastic.
[0028] The gate lines 121 are used to transmit gate signals, and
extend in a horizontal direction. Each of the gate lines 121
includes a plurality of gate electrodes 124 that protrude downward
and an end portion 129 that has a large area so as to be connected
to another layer or an external driving circuit. A gate driving
circuit (not shown) for generating the gate signals may be mounted
on a flexible printed circuit film (not shown) attached on the
substrate 110, may be directly mounted on the substrate 110, or may
be integrated into the substrate 110. When the gate driving circuit
is integrated into the substrate 110, the gate lines 121 may extend
so as to be directly connected to the gate driving circuit.
[0029] A predetermined voltage is applied to each of the storage
electrode lines 131. Each of the storage electrode lines 131
includes a main line extending substantially parallel to the gate
lines 121 and several pairs of first and second storage electrodes
133a and 133b branched from the line. Each of the storage electrode
lines 131 is provided between two gate lines 121 adjacent to each
other, and the main line is closer to the lower one of the two gate
lines 121. Each of the storage electrodes 133a and 133b includes a
fixed end connected to the main line and a free end opposite to the
fixed end. The fixed end of the first storage electrode 133a has a
large area, and the free end thereof is branched into two parts,
that is, a linear part and a curved part. However, the shape and
disposition of each storage electrode line 131 may be modified in
various ways.
[0030] The gate lines 121 and the storage electrode lines 131 may
be made of an aluminum-based metal such as aluminum (Al) or an
aluminum alloy, a silver-based metal such as silver (Ag) or a
silver alloy, a copper-based metal such as copper (Cu) or a copper
alloy, a molybdenum-based metal such as molybdenum (Mo) or a
molybdenum alloy, chromium (Cr), tantalum (Ta), or titanium (Ti).
Meanwhile, each of the gate lines and storage electrode lines may
also have a multi-layered structure that includes two conductive
layers (not shown) with different physical properties.
[0031] The side surfaces of the gate lines 121 and the storage
electrode lines 131 are inclined with respect to the substrate 110,
and it is preferable that an angle of inclination between each side
surface and the substrate is in the range of about 30 to
80.degree..
[0032] A gate insulating layer 140, which is made of silicon
nitride (SiNx) or silicon oxide (SiOx), is formed on the gate lines
121 and the storage electrode lines 131.
[0033] A plurality of semiconductor stripes 151 made of
hydrogenated amorphous silicon (referred to as "a-Si") or
polysilicon are formed on the gate insulating layer 140. The
semiconductor stripes 151 extend substantially in a vertical
direction, and include a plurality of projections 154 protruding
toward the gate electrodes 124. Each of the semiconductor stripes
151 has a large width in the vicinity of the gate lines 121 and the
storage electrode lines 131 so as to cover the gate lines 121 and
the storage electrode lines 131.
[0034] A plurality of ohmic contact stripes and islands 161 and 165
are formed on the semiconductors 151. The ohmic contacts 161 and
165 may be made of n+ hydrogenated amorphous silicon in which
n-type impurities, such as phosphorus, are doped at high
concentration, or of silicide. The ohmic contact stripes 161
include a plurality of protrusions 163, and the protrusions 163 and
the ohmic contact islands 165 are provided in pairs on the
projections 154 of the semiconductors 151.
[0035] The side surfaces of the semiconductors 151 and 154 and the
ohmic contacts 161 and 165 are inclined with respect to the
substrate 110, and an angle of inclination between the side surface
and the substrate 110 is in the range of about 30 to
80.degree..
[0036] A plurality of data lines 171 and a plurality of drain
electrodes 175 are formed on the ohmic contacts 161 and 165 and the
gate insulating layer 140.
[0037] The data lines 171 are used to transmit data signals, and
extend substantially in a vertical direction so as to cross the
gate lines 121 and the storage electrode lines 131. Each of the
data lines 171 also crosses the storage electrode lines 131, and is
provided between the storage electrodes 133a and 133b adjacent to
each other. Each of the data lines 171 includes a plurality of
source electrodes 173 that extend toward the gate electrodes 124
and an end portion 179 that has a large area so as to be connected
to another layer or an external driving circuit. A data driving
circuit (not shown) for generating data signals may be mounted on a
flexible printed circuit film (not shown) attached on the substrate
110, may be directly mounted on the substrate 110, or may be
integrated into the substrate 110. When the data driving circuit is
integrated into the substrate 110, the data lines 171 may extend so
as to be directly connected to the data driving circuit.
[0038] The drain electrodes 175 are separated from the data lines
171, and face the source electrodes 173 with the gate electrodes
124 therebetween. Each of the drain electrodes 175 includes one end
portion having a large width and the other end portion having a bar
shape. The one end portion having a large width overlaps the
storage electrode 137, and the other end portion having a bar shape
is partially surrounded by the bent source electrodes 173.
[0039] A gate electrode 124, a source electrode 173, a drain
electrode 175, and a projection 154 of the semiconductor 151 form a
thin film transistor (TFT), and a channel of the thin film
transistor is provided to the projection 154 between the source
electrode 173 and the drain electrode 175.
[0040] The data line 171 and the drain electrode 175 may be made of
a refractory metal, such as molybdenum, chromium, tantalum, or
titanium, or an alloy thereof, and they may have a multi-layered
structure having a refractory metal layer (not shown) and a
low-resistance conductive layer (not shown). A two-layered
structure having a lower chromium or molybdenum (alloy) layer and
an upper aluminum (alloy) layer, and a three-layered structure
having a lower molybdenum (alloy) layer, an intermediate aluminum
(alloy) layer, and an upper molybdenum (alloy) layer may be used as
an example of the multi-layered structure. However, the data lines
171 and the drain electrodes 175 may be made of various metallic
materials or conductors other than the above metallic
materials.
[0041] It is preferable that the side surfaces of the data lines
171 and the drain electrodes 175 are inclined with respect to the
substrate 110, and an angle of inclination between the side surface
and the substrate is in the range of about 30 to 80.degree..
[0042] The ohmic contacts 161 and 165 are provided only between the
semiconductors 151 and 154 and the data lines 171 and drain
electrodes 175, and they lower the contact resistance between the
semiconductors and the data lines and drain electrodes. The
semiconductor stripes 151 are narrower than the data lines 171 at
most positions. However, as described above, the semiconductor
stripes 151 have large widths at the intersections between the gate
lines 121 and the semiconductor stripes 151 so as to have smooth
surface profiles. Accordingly, it is possible to prevent the data
lines 171 from being disconnected. The semiconductors 151 and 154
have portions not covered with the data lines 171 and the drain
electrodes 175 so as to be exposed to the outside, as well as
portions between the source electrodes 173 and the drain electrodes
175.
[0043] A passivation layer 180 is formed on the data lines 171, the
drain electrodes 175, and the portions of the semiconductors 151
and 154 exposed to the outside. The passivation layer 180 may be
made of an inorganic or organic insulator, and may have a flat
surface. Silicon nitride or silicon oxide may be used as an example
of the inorganic insulator. The organic insulator may have
photosensitivity, and it is preferable that the dielectric constant
of the organic insulator is 4.0 or less. However, the passivation
layer 180 may have a dual-layered structure, which includes a lower
inorganic layer and an upper organic layer, to improve
characteristics of the organic film and to protect the exposed
semiconductors 151 and 154.
[0044] The passivation layer 180 includes a plurality of contact
holes 182 and 185 that expose the end portions 179 of the data
lines 171 and the drain electrodes 175, respectively. Furthermore,
each of the passivation layer 180 and the gate insulating layer 140
includes a plurality of contact holes 181 that expose the end
portions 129 of the gate lines, 121, a plurality of contact holes
183a that partially expose the storage electrode lines 131 in the
vicinity of the fixed end of the first storage electrodes 133a, and
a plurality of contact holes 183b that expose the protrusions of
the free ends of the first storage electrodes 133a.
[0045] A plurality of pixel electrodes 191, a plurality of
overpasses 83, and a plurality of contact assistants 81 and 82 are
formed on the passivation layer 180. Each of the pixel electrodes,
overpasses, and contact assistants may be made of a transparent
conductive material such as ITO or IZO.
[0046] The pixel electrodes 191 are physically and electrically
connected to the drain electrodes 175 through the contact holes
185, and data voltages are applied to the pixel electrodes 191 from
the drain electrodes 175. The pixel electrodes 191 to which the
data voltages are applied generate an electric field together with
a common electrode 270 of a color filter display panel to which a
common voltage is applied, so as to determine the alignment
direction of the liquid crystal molecules of the liquid crystal
layer 3 interposed between the electrodes 191 and 270. The
polarization of light passing through the liquid crystal layer 3
depends on the alignment direction of the liquid crystal molecules
determined as described above. The pixel electrode 191 and the
common electrode 270 form a capacitor (hereinafter referred to as a
"liquid crystal capacitor"), and maintain an applied voltage even
after the thin film transistor is turned off.
[0047] The pixel electrode 191 and the drain electrode 175
connected to the pixel electrode 191 overlap the storage electrodes
133a and 133b and the storage electrode line 131. Further, the left
and right sides of the pixel electrode 191 are closer to the data
line 171 than the storage electrodes 133a and 133b. The pixel
electrode 191 and the drain electrode 175 electrically connected to
the pixel electrode 191 overlap the storage electrode line 131 so
as to form a capacitor. The capacitor is referred to as a storage
capacitor, and the storage capacitor improves the voltage holding
performance of the liquid crystal capacitor.
[0048] The contact assistants 81 and 82 are connected to the end
portion 129 of the gate line 121 and the end portion 179 of the
data line 171 through the contact holes 181 and 182, respectively.
The contact assistants 81 and 82 improve the adhesive property
between the end portion 129 of the gate line 121 and an external
device, and between the end portion 179 of the data line 171 and an
external device. Further, the contact assistants 81 and 82 protect
the end portion 129 of the gate line 121 and the end portion 179 of
the data line 171.
[0049] The overpass 83 crosses the gate line 121, and is connected
to the exposed portion of the storage electrode line 131 and the
end portion of the free end of the storage electrode 133b through
the contact holes 183a and 183b that are positioned on the both
sides of the gate line 121. The storage electrodes 133a and 133b,
the storage electrode line 131, and the overpass 83 may be used to
repair a defective gate line 121, data line 171, or thin film
transistor.
[0050] The color filter array panel 200 will be described
below.
[0051] A light blocking member 220 is formed on an insulation
substrate 210 made of, for example, transparent glass or plastic.
The light blocking member 220 is also called a black matrix, and it
defines a plurality of opening regions facing the pixel electrodes
191 and prevents light from leaking between the pixel electrodes
191.
[0052] In addition, a plurality of color filters 230 are formed on
the substrate 210 so that almost all the color filters are disposed
in the opening regions surrounded by the light blocking member 220.
The color filters 230 are arrayed in stripe shapes along the pixel
electrodes 191 in a vertical direction. Each of the color filters
230 can display one of three primary colors of red, green, and
blue.
[0053] A planarization layer 250 is formed on the color filter 230
and the light blocking member 220, and the common electrode 270 is
formed on the planarization layer 250. It is preferable that the
common electrode 270 is made of a transparent conductive material
such as ITO or IZO.
[0054] It is preferable that the liquid crystal layer 3 is formed
of liquid crystal 31, which has positive refractive anisotropy, in
an electrically controlled birefringence (ECB) mode, and that
alignment layers 11 and 21 for aligning the liquid crystal layer 3
are formed on the inner surfaces of the display panels 100 and 200.
Since each of the alignment layers 11 and 21 is a horizontal
alignment layer, the liquid crystal 31 is laid between the lower
alignment layer 11 and the upper alignment layer 21 in a horizontal
direction. Further, the liquid crystal 31 is aligned in parallel
without rotation, unlike a twisted nematic (TN) liquid crystal.
Accordingly, when a voltage is not applied, the liquid crystal 31
in the electrically controlled birefringence mode is horizontally
aligned in parallel with the substrates. When a voltage is applied,
the liquid crystal 31 in the electrically controlled birefringence
mode is vertically aligned.
[0055] A lower polarizer 12 and an upper polarizer 22 are attached
to the outer surfaces of the display panel 100 and 200,
respectively, and a wide view polarizer 13 is interposed between
the lower polarizer 12 and the thin film transistor array panel
100. Each of the upper polarizer 22, the lower polarizer 12, and
the wide view polarizer 13 has an absorption axis. Further, each of
the upper polarizer 22, the lower polarizer 12, and the wide view
polarizer 13 absorbs polarized light parallel to the absorption
axis, and transmits polarized light perpendicular to the absorption
axis.
[0056] FIG. 4 shows the detailed structure of a liquid crystal
panel including display panels 100 and 200 and a liquid crystal
layer 3 interposed therebetween, a lower polarizer 12, a wide view
polarizer 13, and an upper polarizer 22.
[0057] As shown in FIG. 4, the upper polarizer 22 includes a
polarization medium (polyvinyl alcohol, PVA) 51 and supporters
(triacetate cellulose, TAC) 52. The polarization medium 51 controls
the amount of transmitted light on the basis of the polarized
light, and the supporters 52 are attached at both sides of the
polarization medium 51 to protect and support the polarization
medium 51. A passivation film may be formed on the upper polarizer
22 by an anti-glare process, an anti-reflection process, an
anti-scratch process, or a hard coating process. An adhesive 53 is
provided between the upper polarizer 22 and the liquid crystal
panel 1 so that the upper polarizer 22 and the liquid crystal panel
1 are attached to each other. A pressure sensitive adhesive (PSA)
may be used as the adhesive 53. When the pressure sensitive
adhesive is used as the adhesive 53, objects are slightly pressed
against each other so as to be attached to each other.
[0058] The lower polarizer 12 has a structure in which supporters
(TAC) 62 are attached at both sides of a polarization medium (PVA)
61, and the wide view polarizer 13 has a structure in which a
compensation film 65 is attached to a wide view supporter (WV TAC)
64. WV film series of Fuji film may be used as the wide view
supporter (WV TAC) 64. An adhesive 63 is provided between the lower
polarizer 12 and the wide view polarizer 13, and between the wide
view polarizer 13 and the liquid crystal panel 1 so that the lower
polarizer 12 and the wide view polarizer 13 are attached to each
other and the wide view polarizer 13 and the liquid crystal panel 1
are attached to each other. A pressure sensitive adhesive (PSA) may
be used as the adhesive 63. A passivation film may be formed on the
lower polarizer 12 by an anti-glare process, an anti-reflection
process, an anti-scratch process, or a hard coating process.
[0059] Further, the compensation film 65 may be formed of a
discotic liquid crystal (DLC) coating film, and discotic liquid
crystal molecules are vertically aligned on one surface of the
substrate and horizontally aligned on the other surface of the
substrate in the same direction. The liquid crystal molecules are
continuously arrayed between both substrates every 90.degree., and
an O-plate is typically used as the compensation film 65.
[0060] The compensation film 65 delays phases to ensure a viewing
angle and to solve a problem of gray reversal.
[0061] FIG. 5 is a perspective view illustrating the angular
relationship between the polarizer and the alignment layer shown in
FIGS. 2 and 4, and FIG. 6 is a view illustrating the angular
relationship of a liquid crystal display shown in FIG. 5, as seen
from above.
[0062] In FIGS. 5 and 6, line A means a direction of an absorption
axis of the upper polarizer 22, and line B means a direction of an
upper rubbing axis of the upper alignment layer 21. Further, line
A' means a direction of an absorption axis of the lower polarizer
12, line B' means a direction of a lower rubbing axis of the lower
alignment layer 11, and line C' means a direction of an absorption
axis of the wide view polarizer 13.
[0063] The absorption axis A of the upper polarizer 22 is parallel
to a horizontal direction, and the absorption axis A' of the lower
polarizer 12 is inclined with respect to the horizontal direction
by 90.degree.. For this reason, the absorption axis A of the upper
polarizer 22 is orthogonal to the absorption axis A' of the lower
polarizer 12.
[0064] The upper rubbing axis B is inclined with respect to the
horizontal direction by 45.degree. in a clockwise direction, and
the lower rubbing axis B' is reversed and parallel to the upper
rubbing axis B.
[0065] Further, the absorption axis C' of the wide view polarizer
13 is reversed and parallel to the lower rubbing axis B'.
Furthermore, the absorption axis C' of the wide view polarizer 13
is inclined with respect to the absorption axis A' of the lower
polarizer 12 by 45.degree..
[0066] Since the wide view polarizer 13 is interposed between the
lower polarizer 12 and the liquid crystal panel 1 as described
above, it is possible to ensure a wide viewing angle and to
compensate gray reversal.
[0067] While a cell gap is adjusted, the difference (.DELTA.nd) in
phase, transmittance, color coordinate in a white state, and
contrast ratio (C/R) are measured in the above-mentioned exemplary
embodiment of the present invention. The measurement results
thereof are shown in Table 1. TABLE-US-00001 TABLE 1 Cell gap
.DELTA.nd Transmittance White x White y C/R 3.4 225.42 0.35119
0.29165 0.31291 712.964 3.5 232.05 0.36397 0.29335 0.31499 953.322
3.6 238.68 0.3759 0.29517 0.31722 1292.35 3.7 245.31 0.38691
0.29714 0.3196 1760.275 3.8 251.94 0.39692 0.29925 0.32212 2354.293
3.9 258.57 0.40589 0.3015 0.3248 2957.11 4 265.2 0.41376 0.30391
0.32764 3289.188 4.1 271.83 0.42049 0.30649 0.33063 3133.289 4.2
278.46 0.42605 0.30923 0.3338 2622.164 4.3 285.09 0.43041 0.31216
0.33713 2043.436 4.4 291.72 0.43353 0.31527 0.34063 1555.894
[0068] As shown in Table 1, when the cell gap is in the range of
3.8 to 4.1, it is possible to obtain the optimal contrast
ratio.
[0069] FIG. 7 is a view illustrating the three-dimensional optical
characteristic obtained from the simulation of an exemplary
embodiment shown in Table 1.
[0070] As shown in FIG. 7, when the contrast ratio (C/R) is 10,
viewing angles are 90.degree., 80.degree., 90.degree., and
80.degree. at upper, lower, left and right sides, respectively.
Accordingly, it is possible to understand that wide viewing angles
are obtained.
[0071] FIG. 8 is a view illustrating the three-dimensional optical
characteristic obtained from measurement using a iconoscope while
the difference (.DELTA.nd) in phase is set to 300.96 in the
exemplary embodiment of the present invention, with a picture
illustrating viewing angles in a black state, a picture
illustrating viewing angles in a white state, and a view
illustrating contrast ratios (C/R).
[0072] As shown in FIG. 8, it is possible to understand that the
viewing angle is wide when the contrast ratio (C/R) is 10. Further,
it is possible to confirm that the same results as the simulation
results are obtained from the measurement.
[0073] As described above, the wide view polarizer 13, of which
absorption axis C' is inclined with respect to the absorption axis
A' of the lower polarizer 12 by 45.degree., is interposed between
the lower polarizer 12 and the liquid crystal panel 1 in a backlit
electrically controlled birefringence (ECB) mode. Accordingly, it
is possible to ensure a wide viewing angle and to compensate gray
reversal.
[0074] FIGS. 9 and 10 show a liquid crystal display according to
another exemplary embodiment of the present invention.
[0075] FIG. 9 is a perspective view illustrating the angular
relationship between a polarizer and an alignment layer of a liquid
crystal panel according to another exemplary embodiment of the
present invention, and FIG. 10 is a view illustrating the angular
relationship of the liquid crystal display shown in FIG. 9, as seen
from above.
[0076] As shown in FIGS. 9 and 10, the wide view polarizer 13 is
interposed between the upper polarizer 22 and the liquid crystal
panel 1, and the absorption axis C' of the wide view polarizer 13
is inclined with respect to the horizontal direction by 135.degree.
in a counterclockwise direction. For this reason, the absorption
axis C' is reversed and parallel to the upper rubbing axis B, and
the absorption axis C' of the wide view polarizer 13 is inclined
with respect to the absorption axis A of the upper polarizer 22 by
45.degree..
[0077] Since the wide view polarizer 13 is interposed between the
lower polarizer 22 and the liquid crystal panel 1 as described
above, it is possible to ensure a wide viewing angle and to
compensate gray reversal.
[0078] In the liquid crystal display according to an exemplary
embodiment of the present invention, the wide view polarizer, of
which absorption axis C' is inclined with respect to the absorption
axis A' of the lower polarizer by 45.degree., is interposed between
the lower polarizer and the liquid crystal panel in a backlit
electrically controlled birefringence (ECB) mode. Accordingly, it
is possible to ensure a wide viewing angle and to compensate gray
reversal.
[0079] In addition, even if a backlit liquid crystal display is
manufactured instead of the liquid crystal display of an
electrically controlled birefringence (ECB) mode, it is possible to
ensure a wide viewing angle and to compensate gray reversal. As a
result, the liquid crystal display has a simpler manufacturing
process as compared to a transflective liquid crystal display.
[0080] While this invention has been described in connection with
what is presently considered to be practical exemplary embodiments,
it will be apparent to those skilled in the art that various
modifications and changes may be made thereto without departing
from the scope and spirit of the invention. Accordingly, it is to
be understood that the invention is not limited to the disclosed
embodiments, but, on the contrary, is intended to cover various
modifications and equivalent arrangements included within the
spirit and scope of the appended claims.
* * * * *